The comments from Sen. Lindsey O. Graham (R) were an unusual case of one Republican Senate panel chairman undercutting another’s work by advising a witness in an ongoing investigation. (J. Scott Applewhite/AP)

The head of the Senate Judiciary Committee encouraged Donald Trump Jr. to invoke his right against self-incrimination and refuse to answer questions from the Senate Intelligence Committee if he complies with the panel’s subpoena for a second closed-door interview.

“You just show up and plead the Fifth and it’s over with,” Sen. Lindsey O. Graham (R-S.C.) told reporters Monday, adding that Trump Jr.’s lawyer would “have to be an idiot” to let him testify again.

“This whole thing is nuts,” Graham continued. “To me, it’s over.”

Graham’s comments, which come just a day after he said on Fox News that Trump Jr. should ignore the summons, could serve as a temporary off-ramp in the standoff between the Intelligence Committee, led by Sen. Richard Burr (R-N.C.), and GOP senators either aligned with the president or up for reelection in 2020. It is also a remarkable display of one Republican Senate panel chairman undercutting another’s work by dispensing free legal advice to a witness in an ongoing investigation — and reflects a greater GOP divide about whether the Senate should hold Trump Jr. in contempt if he continues to flout the Intelligence Committee’s subpoena.

Discussions are ongoing. But already, senior senators such as John Cornyn (R-Tex.), a member of the Intelligence panel, have publicly taken Trump Jr.’s side.

“He’s already testified like nine hours. At some point, I think there’s other ways to address it,” Cornyn said Monday, suggesting that Trump Jr.’s team submit written answers so the panel can avoid being “even more intrusive than we’ve been.”

Yet submitting written answers in lieu of appearing in person was never on the table, according to people familiar with the negotiations with Trump Jr. The Senate Intelligence Committee is scheduling second-round interviews for members to question key witnesses, as the investigation has been largely staff-run. The president’s son-in-law, Jared Kushner, appeared for such an interview in late March.

Last week, Burr detailed to his GOP colleagues the months-long process of trying to secure Trump Jr.’s testimony. According to people familiar with the negotiations and his explanation, Trump Jr. twice agreed to dates in March and April, but as the interviews approached, his lawyers sought to postpone them. The first time, the panel agreed; the second time it did not, and issued a subpoena for his testimony.

A person close to Trump Jr. described the Intelligence panel’s request as “completely unreasonable” on Monday, adding “we are not doing a do-over.”

The panel has not yet revealed the deadline on its subpoena for Trump Jr.’s testimony. But the ultimate arbiter of whether the Senate enforces the summons with contempt proceedings will be Senate Majority Leader Mitch McConnell (R-Ky.).

McConnell has thus far sought to provide political cover for Burr’s probe and last week appealed to Republican senators to let him run the investigation without interference. But the continued defense of Trump Jr. by Graham and others will complicate the prospect of bringing any contempt resolution to the floor.

Looming over the dispute about Trump Jr.’s appearance are questions, particularly from Democrats, about whether he previously lied to lawmakers about telling his father the Trump campaign had been approached by a Russian lawyer offering dirt on Hillary Clinton. Trump Jr. told three congressional panels that he did not tell him.

Yet special counsel Robert S. Mueller III’s report details the recollection of Trump’s former lawyer and fixer Michael Cohen that Trump Jr. called his father to discuss an upcoming meeting to get “adverse information” on Clinton.

Mueller never interviewed the president or his son; Cohen is serving a three-year prison term for financial crimes and lying to Congress.